A disk drive system typically has one or more magnetic recording disks and control mechanisms for storing data within approximately circular tracks on a disk. The magnetic recording disk is composed of a substrate and one or more layers deposited on the substrate. A disk substrate may be produced from a blank sheet of, for example, a metal-based material such as aluminum or aluminum magnesium. The sheet may be punched to generate a disk substrate having an inner diameter (ID) and an outer diameter (OD). After removing the ID and OD, the disk-shaped substrate may be further processed (e.g., polished, textured, layer deposition, etc.) to produce the magnetic recording disk.
The trend in the design of magnetic hard disk drives is to increase the recording density of a disk drive system. Recording density is a measure of the amount of data that may be stored in a given area of disk. One method for increasing recording densities is to pattern the surface of the disk to form discrete tracks, referred to as discrete track recording (DTR). DTR disks typically have a series of concentric raised zones (a.k.a., lands, elevations, etc.) storing data and recessed zones (a.k.a., troughs, valleys, grooves, etc.) that may store servo information. The recessed zones separate the raised zones to inhibit or prevent the unintended storage of data in the raised zones.
One method of producing DTR magnetic recoding disks is through the use of a press to imprint embossable films residing on one or both sides of a disk substrate. The press utilizes a die for each side of the disk to be imprinted. The die includes a stamper that is pressed into the embossable film to form the imprinted pattern in the film. The pattern is subsequently transferred to the substrate and/or one or more layers residing above the substrate. Thin film magnetic recording layers are then sputtered over the patterned surface of the substrate to produce the DTR media having a continuous magnetic layer extending over both the raised zones and the recessed zones.
Conventional presses utilize multiple post precision die sets to attain alignment of the upper and lower dies used to imprint the embossable films on each side of the disk substrate. One problem with conventional presses is that they require specialized press alignment methods involving the use of a mandrel, or shaft, in the upper die. The mandrel is disposed near the middle portion of the upper die and has a tapered nose oriented to face the lower die. The mandrel has a diameter sized to engage the ID of the disk. The lower die has a cylindrical opening sized to receive the tapered nose of mandrel. The upper and lower dies also contain membrane or elastomer backed stampers that are used to imprint the embossable films. The stampers are disposed around the mandrel and, thus, have an annular shape with an inner diameter (i.e., a hole, or cavity, at their centers). The membranes or elastomers provide for compliance or parallelism between the embossable films and the stamper's patterned surface during pressing. One problem with this type of press system configuration is that the contact between the components (e.g., disk, stamper, mandrel, etc.) causes unwanted particulates (e.g., dust and other impurities) to accumulate around or in the components. Contamination of the press system has detrimental effects, including the decay of the membranes and elastomers, and also the damage to the stampers and imprinted disks. In addition, with such a press system, when a particular die portion becomes contaminated, the entire press system or die assembly needs to be shut down in order to service the contaminated die portion. This causes idling of the press system that slows manufacturing cycle times.
Another problem with conventional presses is that they require very robust clamping structures to hold a stamper immobile in a die under high stamping forces. Such clamping structures may be incompatible with the clearances required, for example, for DTR imprinting operations. A stamper used for DTR imprinting operations may need to be unyieldingly held about a central axis, in a flat plane, in order to accurately imprint disks. However, since the two opposing stampers in a press are typically separated by only the thickness of a disk (e.g., 1300 microns or less), there is little room for the sort of robust clamping apparatus need to hold a stamper immobile in a die under high stamping forces.